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Mineral Resources > Online Spatial Data > Geology > by state > Tennessee Geology

Geologic units in McNairy county, Tennessee

Midway Group including Porters Creek Clay and Clayton Formation (Tertiary) at surface, covers 2 % of this area

Midway Group - includes Porters Creek Clay - Pale-brown to brownish-gray, massive, blocky clay; locally contains glauconitic sand. Thickness 130 to 170 feet. Also includes Clayton Formation- Glauconitic sand, argillaceous and locally fossiliferous; at base in Hardeman County is an impure fossiliferous limestone. Thickness 30 to 70 feet.

Lithology: clay or mud; sand; limestone

High-level alluvial deposits (Quaternary-Tertiary) at surface, covers 5 % of this area

High-level Alluvial Deposits - Iron-stained gravel, sand, silt, and clay; variable in thickness but generally less then 60 feet thick.

Lithology: gravel; sand; silt; clay or mud

Alluvial deposits (Quaternary) at surface, covers 17 % of this area

Alluvial Deposits - Sand, silt, clay, and gravel. In flood plain of Mississippi River more than 100 feet thick; in smaller streams generally less than 20 feet thick.

Lithology: sand; silt; clay or mud; gravel

Owl Creek Formation (Cretaceous) at surface, covers 1 % of this area

Owl Creek Formation - Sandy clay, greenish gray, glauconitic, fossiliferous; merges northward into unfossiliferous clays and sands. Thickness 0 to about 40 feet.

Lithology: clay or mud; sand

Claiborne and Wilcox Formation (Tertiary) at surface, covers < 0.1 % of this area

Claiborne and Wilcox Formations -- Irregularly bedded sand, locally interbedded with lenses and beds of gray to white clay, silty clay, lignitic clay, and lignite. Thickness more than 400 feet.

Lithology: sand; clay or mud; lignite

Sardis Formation (Cretaceous) at surface, covers < 0.1 % of this area

Sardis Formation - Quartz sand and glauconite sand, argillaceous and locally fossiliferous. (Mapped with Kcc north of Beech River.) Maximum thickness 70 feet.

Lithology: sand

Coffee Sand (Cretaceous) at surface, covers 3 % of this area

Coffee Sand - Loose fine-grained sand, light-gray, sparsely glauconitic, locally interbedded with laminated lignitic clay. Thickness 25 to 200 feet; thins northward.

Lithology: sand; clay or mud

Coon Creek Formation (Cretaceous) at surface, covers 19 % of this area

Coon Creek Formation - Fossiliferous, micaceous sand, silty and glauconitic; locally fossiliferous sandy clay at base. Siderite concretions common in upper part. Thickness about 140 feet.

Lithology: sand; clay or mud

McNairy Sand (Cretaceous) at surface, covers 42 % of this area

McNairy Sand - Predominantly sand, in places interbedded with silty light-gray clays. Fine-grained sand at base, locally contains heavy minerals. Thickness about 300 feet.

Lithology: sand; clay or mud

Demopolis Formation (Cretaceous) at surface, covers 10 % of this area

Demopolis Formation - Marl and calcareous clay, light-gray, fossiliferous, locally glauconitic and sandy. Merges northward into sands mapped as Kcc. Maximum thickness 180 feet.

Lithology: clay or mud